Hot rolling mill

ABSTRACT

A hot rolling mill and a method of operation to reduce scrap upon failure of a portion of the mill. A first furnace device is provided in the mill adapted to receive and reel up a strip which is ready to go to the finishing section of the mill. A second furnace device is provided to receive a strip of material being rolled in the roughing section of the mill without reeling up. Both furnace devices maintain the material therein at working temperature and in continuous motion.

This is a divisional application of co-pending parent application Ser.No. 756,708, filed Jan. 4, 1977, now abandoned.

The present invention relates to a method for reducing the amount ofscrap caused by disorders in hot band rolling mills, expecially incontinuous hot band rolling mills in which the hot band is rolled out toa pre-bend (Vorband) in a roughing or shaping train to the intakethickness for a subsequent finishing train. The invention furthermorerelates to a hot band rolling mill for practicing this method in acontinuous manner. Such hot band rolling mill comprises primarily apusher furnace, a roughing or shaping train which in rolling directionfollows the pusher furnace and is provided with a scale washer toppingshears (Schopfschere) and finishing stands as well as reels and rollerbeds interconnecting the individual stations of the rolling mill whilebetween the roughing or shaping train and the finishing train there isarranged a band withdrawing device adjacent the roller bed.

In continuously operating hot band rolling mills, more or lessfrequently disorders will occur during which the rolling operation hasto be interrupted. The material which at the time of the disorder hasbeen entirely or partly rolled out has then to be removed from therolling train and can no longer be treated as first quality material,while a considerable portion of this material will have only scrapvalue. If the disorder is of the kind caused at the reels, for instancecaused by a stuck or jammed leading end of a band, there will be a totalof three slabs in the rolling process of a continuous hot band train,which means the financial loss will be considerable although caused byonly a single disorder.

Considering the fact that in hot band rolling mills between the roughingtrain and the finishing train there is provided only a band withdrawingdevice adjacent the rolling bed for a fast removal of a portion of thepre-band and that besides the hall cranes no further devices are presentfor removing the further rolling goods from the rolling train, it willbe evident that considerable time is required to put the rolling trainback into full operation following a disorder.

From German Offenlegungsschrift No. 2,256,024 and GermanOffenlegungsschrift No. 2,256,030 it has become known to provide awinding device ahead of the topping shears of the finishing train whenlooking in rolling direction. Such winding device has been provided toincrease the binding weights. At the same time this known windingdevice, onto which a pre-band is wound up in rolling out direction andis wound off in the same direction, is intended during disorders of therolling train to store the slab rolled out to a pre-band until thedisorder has been remedied. However, inasmuch as the winding device isall the time occupied by a pre-band during the rolling process, it isnot possible that when a disorder suddenly occurs, for instance at thereels, the pre-band just leaving the roughing train is likewise receivedby the winding device. Therefore, this known device cannot meet therequirement as described above. Aside therefrom, it should be noted thatat least with fully continuous or 3/4-continuous hot band trains thereis still a further slab present in the rolling train, namely in thefirst roughing stand of the roughing train.

It is therefore, an object of the present invention to provide a methodof and a rolling mill for carrying out the method by means of which thedrawbacks of the heretofore known methods and devices will be avoided ina simple manner and by means of which the loss in material duringdisorders in hot band trains as well as the duration of the disorders,and last but not least the loss in ourput, will be reduced to a minimum.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawings, in which:

FIG. 1 diagrammatically illustrates a fully continuous hot band train.

FIG. 2 is a diagrammatic illustration of a 3/4-continuous hot bandtrain.

FIG. 3 is a diagrammatic illustration of a half-continuous hot bandtrain.

FIG. 4 illustrates a side view partly in section of a holding furnacewith winding device for use in connection with the present invention.

FIG. 5 is a section through a roller hearth type furnace for use inconnection with the present invention.

FIG. 6 shows the arrangement of a roller hearth type furnace inconnection with a roller bed.

The method according to the present invention is characterized primarilyin that the pre-band is moved back to the roughing train in thedirection counter to the rolling direction, is wound up and held atrolling temperature, and is furthermore characterized in that a pre-slabalready rolled in at least one pass is held at rolling temperature.

According to a further development of the method according to theinvention the wound up pre-band and the pre-slab are, while being heldin hot condition, moved so that a uniform heating through of the rollingmaterial will be obtained.

The continuous rolling mill which is best suited for practicing themethod according to the invention is in conformity with the presentinvention built up in such a way that within the roughing train inrolling direction ahead of the last roughing stand there is provided aholding furnace with a winding device, that further a roller hearth-typefurnace is provided for receiving a pre-slab rolled out in at least onepass, and that in the last roughing stand the lower working roller andthe lower supporting roller are adapted to be lowered. According to apreferred design, the holding furnace comprises a disengageable hoodprovided with a refractory heat insulating lining and resting above theroller bed on a frame provided with a band inlet opening.

According to a preferred embodiment of the invention, the roller hearthtype furnace is arranged within the roughing train between the firstroughing stand and the second roughing stand adjacent the roller bedwhich is located between the roughing stands. If for reasons of spacesuch an arrangement is not possible, the roller hearth type furnace maybe expediently arranged at the end of the roller bed ahead of the firstpusher furnace.

In order to be able to keep the rolling material, which means the woundup shaped band and the slab already rolled in at least one pass, for alonger period of time in the furnace, all rollers in the holding furnaceand in the hearth type furnace are made of refractory material while theaxles are cooled, preferably water cooled.

Referring now to the drawings in detail, FIG. 1 shows a fully continuoushot wide band train, which comprises pusher furnaces 1 (one only beingshown) and furthermore comprises the following units which are arrangedone behind the other in the rolling line: the scale washer 2, theroughing stands 3-7 of the roughing train, he additional scale washer 8,the topping shears 9, the finish stands 10-15 of the finish train, thereels 16-18, and the roller beds 19. In addition to the roller beds 19,between the last roughing stand of the roughing train and the scalewasher 8 arranged ahead of the topping shears 9 there is provided a bandwithdrawing device 20 by means of which one portion of a roughing bandcan be withdrawn from the roller bed 19 which during disorder forinstance in the reels 16-18 is still located outside the first finishstand 10 and has been cut off by the topping shears 9.

The 3/4 continuous hot band train according to FIG. 2 differs from thefully continuous train according to FIG. 1 as to its construction merelyin that only three roughing stands 3, 4, and 7 have been provided whilethe intermediate roughing stand 4 has been designed as reversing stand.

The roughing stand according to FIGS. 1 and 2 is equipped with aso-called back pass device by means of which the lower working roll andthe lower supporting roll can be lowered.

In a corresponding manner, with a semi-continuous hot band trainaccording to FIG. 3, the only roughing stand of the roughing train isdesigned as reversing stand 21.

According to the embodiments of hot band trains according to FIGS. 1-3,within the roughing train starting with the scale washer 2 and endingwith the last roughing stand 7, 21 and more specifically in the rollingdirection ahead of the roughing stand 7, 21 there is provided a hotkeeping furnace 22 with a winding device according to FIG. 4. Thefurnace 22 according to FIG. 4 comprises a detachable hood 23 which isequipped with a refractory heat insulating lining 24 and rests on aframe 25 which is mounted above the roller bed 19 and is provided with aframe 25 having an inlet opening. In a support 26 arranged on the frame25 there is provided a winding device which comprises a rotatablemandrel 29 and a driven supporting roller pair 30. The mandrel 29 servesexclusively for centering the bundles in the furnace 22 and does nottake part in the winding operation. A side wall of the hood 23 isexpediently designed as door in order if necessary to remove a bundle.

If a disorder occurs in a hot band train, the band in the finishingtrain is removed in a manner known per se by means of the bandwithdrawing device 20 or the crane, and the roughing slab in theroughing train is in customary manner finish rolled to the roughingthickness required for the finishing train. After leaving the lastroughing stand 7, 21 as seen in rolling direction, the roughing band isby means of the roughing stand 7, 21 moved backwards counter to therolling direction. To this end, advantageously the rollers of the rollerbed section 19c between the topping shears 9 and the hot holding furnace22 are reversible in their direction of rotation. The roughing bandpasses via the roller bed section 19a which is adapted to be lifted andlowered by means of a cylinder piston system 31, through the drivingroller pair 27 into the three-roller bending unit 28 in which it is bentupwardly around the mandrel 29 and is subsequently wound up. The finishwound roughing band is supported by the supporting roller pair 30 andduring its staying time in the hot keeping furnace is slowly turned forinstance at a speed of 0.5 rpm.

Heating bodies 32 are arranged in the refractory lining 24 of the hood23 and also in the rotatable mandrel 29, said heating bodies beinguniformly distributed about the axis of the mandrel and arranged inrecesses. Further heating bodies 33 are arranged ahead of the two endfaces of the wound up roughing band in the side walls of the furnace. Assoon as a disorder occurs in the rolling mill, the heating bodies areturned on, and the band is kept at rolling temperature, in order toprevent a scaling of the roughing band surface in the hot keepingfurnace 22, the interior of the furnace is for the band staying timefilled with inert protective gas, for instance nitrogen. To this end, inthe hood 23 filling connections 34 as well as a non-illustrated closureflap for the inlet opening are provided on frame 25.

For purposes of unwinding the roughing band from the hot keeping furnace22, the supporting block 26 has connected thereto a pivotable wedge 26aas well as a guiding rail 26b. By means of the wedge 26a, the leadingend of the band is lifted off from the bundle and is introduced by theguiding rail 26b into the three-roller bending unit 28.

When a disorder occurs within the region of the reel 16-18, in a fulland also a 3/4 continuous hot band train, the third slab being processedis just subjected to the first pass in the roughing stand 3. Forpurposes of keeping this slab for the time period of the disorder in therolling mill, there is provided a roller hearth-like furnace 35according to FIGS. 5 and 6 between the first roughing stand 3 and thesecond roughing stand 4, said furnace 35 being arranged adjacent theroller bed section 19b.

As will be seen from FIG. 5, the roller hearth-like furnace 35 comprisesprimarily the rollers 36 arranged in the furnace bottom, and driven andcooled by motors 36a, and furthermore comprises the detachable furnacecover 37 and the laterally arranged pendulum pushers (vorstossen) 38. Inthe furnace cover 37 as well as in the furnace bottom, heat bodies 39are provided in recesses. Between the rollers 36, guiding means 40 of ahook dragging device 41 are arranged which are introduced into theroller bed section 19b and are arranged between two roller bed rollers.By means of the hook dragging device 41, the slab which in the roughingstand 3 has received the first pass is by means of roller bed section19b pulled into the roller hearth-like furnace 35.

The hook dragging device 41 (FIG. 6) comprises a motor 42 and atransmission 43 with a shaft 44 by means of which the non-illustratedhook dragging means is synchronously moved for instance by chains orcables.

During the stay of the slab in the roller hearth-like furnace 35 whilethe furnace is provided with a protective gas filling, the heatingbodies 39 are turned on which are likewise designed as radiation orinduction heating bodies. During this time, the slab is within thefurnace 35 subjected by rollers 36 to a reciprocatory pendulum movement.

After the disorder in the rolling mill has been remedied, first theroughing band kept at the rolling temperature is again unwound from thehot keeping furnace 22 into the rolling direction and by means of theroughing stand 7, 21, is fed to the finishing stands 10-15 for a furtherrolling operation. In the meantime, the slab kept hot in the rollerhearth-like furnace 35 is by means of the hook dragging device 41 againmoved onto the roller bed section 19b and directly subsequently theretois rolled further in the roughing train.

As will be evident from the above, the advantages of the method and hotband rolling mill according to the invention consist primarily in thatin a simple manner, the loss in material during disorders in the hotband trains, the duration of the period of disorder, and the loss inoutput can be reduced to a minimum.

It is, of course, to be understood that the present invention is, by nomeans, limited to the specific showing in the drawings, but alsocomprises any modifications within the scope of the appended claims.

We claimed:
 1. A hot rolling mill for rolling a continuous wide band ofmetal along a substantially linear working path, said mill comprising aplurality of sequentially arranged processing units including a pusherfurnace means, a multiple stand roughing section following said pusherfurnace means and including a scale washer, a multiple stand finishingsection following the roughing section, a reeling up section followingthe finishing section, shear means at an inlet end of said finishingsection, roller beds interposed between said sections for conveying theband therebetween and band withdrawing means preceding said shear meansfor withdrawing a roughed band of material from the finishing section, afirst furnace device positioned upstream of a final roughing stand ofsaid roughing section, and provided with reeler means for reeling up aroughed band of material about a horizontal axis and maintaining theworking temperature of said roughed band of material supplied thereto ina reverse rolling direction along said working path from said finalroughing stand, and a second furnace device disposed laterally of theworking path of said mill and following at least a first stand of theroughing section and adapted to receive a roughed slab of material andto maintain the roughed slab rolled in said roughing section at workingtemperature, and means for moving said roughed slab laterally betweensaid working path of the mill and said second furnace device.
 2. Arolling mill according to claim 1 in which the rollers of said finalroughing stand are vertically movable.
 3. A rolling mill according toclaim 1 in which said first furnace device comprises an insulated hoodwithin which said roughed band supplied thereto is reeled up, said hoodhaving an opening in the bottom for movement of said roughed band to andfrom said first furnace device.
 4. A rolling mill according to claim 3in which a stationary support is provided within the hood, feed rollersadjacent said opening for driving said roughed band into said firstfurnace, a set of bending rollers adjacent said feed rollers, a mandrelfor reeling the said roughed band, a pair of driven support rollers tosupport said reeled roughed band of material, and guide strip means toguide said roughed band and disposed between said mandrel and saidbending rollers and including a movable guide strip having an endadapted to engage said roughed band as it is withdrawn from the mandreland driven from said first furnace.
 5. A rolling mill according to claim3 which includes heating means surrounding the reeled roughed band bothcircumferentially and axially and on both the inside and outside of saidreeled roughed band.
 6. A rolling mill according to claim 3 whichincludes means for supplying a nonreactive gas to the inside of saidhood.
 7. A rolling mill according to claim 3 in which said hood includesa side door for access to the interior thereof.
 8. A rolling millaccording to claim 1 in which said second furnace device is disposedbeside the work path of the mill between said first stand and a secondstand of the roughing section of the mill.
 9. A rolling mill accordingto claim 1 which includes a roller bed between said first stand and asecond stand of the roughing section of the mill and said second furnacedevice is located laterally of said roller bed.
 10. A rolling millaccording to claim 9 in which said second furnace device has a bed withdriven rollers therein, a detachable cover for said second device, andoscillatory support pushers for said cover.
 11. A rolling mill accordingto claim 9 which includes means for supplying a nonreactive gas to saidsecond furnace device.
 12. A rolling mill according to claim 10 whichincludes heating bodies in said bed and said cover for supplying heat tosaid roughed slab therein.
 13. A rolling mill according to claim 12 inwhich said bodies comprise at least one of radiation and inductionheating bodies.
 14. A rolling mill according to claim 9 which includeslaterally extending drag conveyor means for moving said roughed slab ofmaterial between said second furnace device and the working path of themill.
 15. A rolling mill according to claim 14 in which said dragconveyor means includes a drive motor, a transmission having an outputshaft, hook means driven by said output shaft, and guide means for saidhook means extending laterally from said second device into said rollerbed.
 16. A rolling mill according to claim 1 in which each of said firstand second furnace devices include rollers, said rollers being formed ofheat resistant material and having axles, and means for cooling saidaxles.